The present invention relates to devices and methods for detecting evidence at, for example, the scene of a crime. More particularly, it relates to devices and methods for detecting fluorescent substances and other materials or features which may be made fluorescent, such as fingerprints.
The detection of objects or features not normally visible to the human eye has long been recognized as a significant problem, especially in the field of law enforcement where detection of evidence is of critical importance. In this field the effort has focused on the improvement of the detection of fingerprints.
Devices and methods for detecting fingerprints frequently use lasers because of the laser's high detection rate. The laser excites fluorescent substances carried by the fingerprint making the fingerprint visible. The laser may excite fluorescent substances in the fingerprint residue itself, or fluorescent substances deposited on and carried by the fingerprint such as powders, dyes or chemical reagents. Such devices may also be used to detect fluorescent evidence other than fingerprints such as certain fibers and sweat. See, for example, U.S. Pat. Nos. 4,708,882 and 4,794,260 to Asano, et al.
Lasers, however, present new problems to the crime scene investigator. Their portability is extremely limited and they may be unwieldy in confined spaces because they require a large power supply which must be transported to the scene. They may also be unsafe to operate because the laser beam itself is hazardous and caution must be taken so that it does not reach the human eye either directly or by reflection.
Fingerprints may, of course, be detected without lasers by using dusting powders, fuming and chemical reagents. Viewing may be enhanced by the use of ultraviolet light. See, for example, U.S. Pat. No. 4,504,408 to Morton. These techniques, however, generally have lower success rates than laser detection techniques. Old prints and prints on porous materials are particularly difficult to detect.
It is accordingly an object of the present invention to provide a novel device and method for detecting evidence, including fingerprints, that obviates the problems of the prior art and is portable and safe to use.
It is another object of the present invention to provide a novel device for detecting evidence, including fingerprints, without a laser, but with a relatively high degree of success.
It is yet another object of the present invention to provide a novel device for detecting evidence that illuminates fluorescent evidence with noncoherent light and detects the wavelength-shifted reflection from the evidence with a light intensifier.
It is still another object of the present invention to provide a novel device for detecting fluorescent evidence without lasers that uses light filters having non-overlapping bandwidths for forming an image of the fluorescent evidence.
It is a further object of the present invention to provide a novel method for detecting fluorescent evidence without laser that includes illuminating the evidence with a specifically filtered light and detecting and intensifying the wavelength-shifted reflection from the evidence.
It is yet a further object of the present invention to provide a novel method for detecting fingerprints using reflections of noncoherent light filtered so that only the images of the fingerprints are received and intensified.
It is still a further object of the present invention to provide an apparatus which can be used by police and similar departments for plural purposes in the investigation of crime scenes and criminal activity.
These and many other objects and advantages will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.